Display including emission layer

ABSTRACT

A display capable of preventing an emission layer from deterioration resulting from temperature rise of an electrode also when the same is increased in size and easily connectable with an external current source also when the same is connected with the external current source on a single portion is provided. This display comprises a first electrode formed on a substrate, an emission layer formed on the first electrode, a second electrode formed on the emission layer, a peripheral electrode, arranged to enclose the outer periphery of the second electrode and connected with at least three edges of the outer periphery of the second electrode, having a smaller sheet resistance value than the second electrode, and a current source connection terminal connected to the outer periphery of the peripheral electrode. Thus, current readily flows from the second electrode toward the peripheral electrode, while the current can be dispersedly fed along three or four directions.

RELATED APPLICATIONS

This application is a divisional of application Ser. No. 10/252,834,filed Sep. 24, 2002, now U.S. Pat. No. 7,151,340 which claims priorityof Japanese Patent application No. JP2001-298739, filed Sep. 28, 2001,the contents of which are herewith incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display, and more specifically, itrelates to a display including an emission layer such as an organiclayer.

2. Description of the Background Art

Requirement for flat display devices exhibiting smaller powerconsumption than a generally employed CRT is recently increasedfollowing diversification of information apparatuses. Among such flatdisplay devices, a display employing an organic electroluminescenceelement (hereinafter referred to as an organic EL element) characterizedby high efficiency, thinness/lightweight property and no view angledependency is actively researched and developed.

FIG. 12 is a perspective view showing the overall structure of aconventional organic EL display. FIG. 13 is a plan view of theconventional organic EL display shown in FIG. 12. Referring to FIGS. 12and 13, anodes 102 of ITO (indium-tin oxide) are formed on a glasssubstrate 101 in the conventional organic EL display. Organic layers 105including hole injection layers, hole transport layers and emissionlayers are formed on the anodes 102. A cathode 103 is formed on theorganic layers 105. This cathode 103 is provided with an outlet terminal104.

Drive circuits 106 a and 106 b are formed on the glass substrate 101.Video signal lines 151 are connected to the drive circuit 106 a.Scanning lines 152 and power supply lines 153 are connected to the drivecircuit 106 b. The outlet terminal 104 of the cathode 103 is connectedto a current supply input terminal 108 for supplying current from acurrent source. The cathode 103 is formed to cover a plurality ofpixels. Therefore, current for driving the plurality of pixelsconcentrically flows into the cathode 103.

As hereinabove described, the current for driving the plurality ofpixels flows into the cathode 103 in the conventional organic ELdisplay. In this case, the current concentrates to the outlet terminal104 of the cathode 103, disadvantageously leading to resistance heatingof the outlet terminal 104. Particularly when the organic EL display isincreased in size, large current flows to the outlet terminal 104 toincrease resistance heating thereof.

When resistance heating of the outlet terminal 104 is increased, thetemperature of the cathode 103 is increased to disadvantageouslydeteriorate the organic layers 105 located under the cathode 103.

In general, therefore, various methods are proposed in order to suppressheat generation in an outlet terminal part. For example, Japanese PatentLaying-Open No. 2001-109398 proposes a structure increasing the width ofan outlet terminal part.

Even if the width of a single outlet terminal part is increased,however, large current concentrically flows to the single outletterminal part when the display is increased in size, and hence it isdifficult to reduce the quantity of heat generation in the outletterminal part. When the display is increased in size, therefore, it isso difficult to reduce temperature rise of a cathode that it is alsodifficult to prevent organic layers from deterioration resulting fromtemperature rise of the cathode.

Japanese Patent Laying-Open No. 2001-85158 discloses a technique ofincreasing the width of outlet terminal (drawing terminal) parts of acathode (second electrode) while providing the outlet terminal parts ontwo portions of opposite edges. In general, however, connection with anexternal current source is performed on a single portion and hence it isdifficult to connect the outlet terminals of the cathode (secondelectrode) with the external current source when the outlet terminalsare provided on two portions of the opposite edges. In the structuredisclosed in the aforementioned gazette, further, current can bedispersed to the two outlet terminals (two directions) of the cathode.However, it is difficult to disperse the current in three or fourdirections. When large current flows in a display increased in size,therefore, it is difficult to disperse the current for inhibiting thecathode from heat generation.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a display capable ofpreventing an emission layer (organic layer) from deteriorationresulting from temperature rise of an electrode also when the display isincreased in size and easily connectable with an external current sourcealso when the display is connected with the external current source on asingle portion.

Another object of the present invention to inhibit a current sourceconnection terminal connected with the external current source fromtransferring heat to the electrode in the aforementioned display.

In order to attain the aforementioned objects, a display according to anaspect of the present invention comprises a first electrode formed on asubstrate, an emission layer formed on the first electrode, a secondelectrode formed on the emission layer, a peripheral electrode, arrangedto enclose the outer periphery of the second electrode and connectedwith at least three edges of the outer periphery of the secondelectrode, having a smaller sheet resistance value than the secondelectrode, and a current source connection terminal connected to theouter periphery of the peripheral electrode.

The display according to this aspect is provided with the peripheralelectrode, arranged to enclose the outer periphery of the secondelectrode and connected with at least three edges of the outer peripheryof the second electrode, having a smaller sheet resistance value thanthe second electrode as hereinabove described, whereby current readilyflows from the second electrode toward the peripheral electrode and thiscurrent can be dispersedly fed in three or four directions. Thus, heatgeneration of the second electrode can be further suppressed as comparedwith a case of dispersedly feeding the current along two directions ofthe second electrode. Consequently, the emission layer can beeffectively prevented from deterioration resulting from heat generation(temperature rise) of the second electrode also when the display isincreased in size. The current source connection terminal is connectedto the outer periphery of the peripheral electrode arranged to enclosethe outer periphery of the second electrode so that the second electrodeand the single current source connection terminal can be easilyelectrically connected with each other through the peripheral electrode.Consequently, the display can be easily connected with the externalcurrent source through the single current source connection terminalalso when connected with the external current source on a singleportion. The current source connection terminal is provided on the outerperiphery of the peripheral electrode for increasing the distancebetween the current source connection terminal and the second electrodeby the width of the peripheral electrode, whereby heat generated in thecurrent source connection terminal is hardly transferred to the secondelectrode. Thus, the second electrode is inhibited from temperaturerise, whereby the emission layer can be inhibited from deteriorationresulting from temperature rise of the second electrode.

In the display according to the aforementioned aspect, the peripheralelectrode may be annularly formed. Further, the peripheral electrode maybe formed to be in contact with the side surface of the outer peripheryof the second electrode. The peripheral electrode having a smaller sheetresistance value than the second electrode preferably contains at leastone of Mg, Ti and Al. When employing such a material, the peripheralelectrode having a smaller sheet resistance value than the secondelectrode can be easily formed. Further, only a single current sourceconnection terminal may be provided.

In the display according to the aforementioned aspect, the peripheralelectrode is preferably connected with three edges of the secondelectrode other than an edge of the second electrode corresponding to anedge of the peripheral electrode connected with the current sourceconnection terminal, and an opening is preferably formed between theedge of the peripheral electrode connected with the current sourceconnection terminal and the corresponding edge of the second electrode.According to this structure, heat generated in the current sourceconnection terminal is further hardly transferred to the secondelectrode, due to the opening. Thus, the emission layer can be furtherinhibited from deterioration resulting from temperature rise of thesecond electrode.

In the display according to the aforementioned aspect, the contact areabetween the second electrode and the peripheral electrode is preferablyincreased as receding from the current source connection terminal.According to this structure, the second electrode can be furthereffectively prevented from transfer of heat readily generated in thecurrent source connection terminal. Thus, the second electrode can beprevented from temperature rise, whereby the emission layer can beprevented from deterioration resulting from temperature rise of thesecond electrode.

In this case, an opening is preferably formed in an edge of the secondelectrode closest to the current source connection terminal, two edgesof the second electrode secondly closest to the current sourceconnection terminal are preferably in contact with corresponding edgesof the peripheral electrode through a plurality of outlet terminalsprovided on the two edges of the second electrode, and an edge of thesecond electrode farthest from the current source connection terminal ispreferably totally in contact with a corresponding edge of theperipheral electrode. According to this structure, the second electrodeand the peripheral electrode are in contact with each other on threeedges of the second electrode and corresponding three edges of theperipheral electrode, whereby current dispersedly flows from the secondelectrode toward the peripheral electrode along three directions. Thus,heat generation of the second electrode can be further suppressed ascompared with a case where the current dispersedly flows along twodirections of the second electrode. Thus, the emission layer can beprevented from deterioration resulting from temperature rise of thesecond electrode. In this case, the plurality of outlet terminals may beformed by projecting portions of irregular shapes provided on the twoedges of the second electrode secondly closest to the current sourceconnection terminal.

In the display according to the aforementioned aspect, the peripheralelectrode is preferably formed to be connected with four edges of theouter periphery of the second electrode. According to this structure,current can be uniformly dispersedly fed from the second electrodetoward the peripheral electrode along four directions. Thus, thequantity of heat generated in the second electrode can be reduced ascompared with a case where the current dispersedly flows along twodirections of the second electrode.

In the aforementioned structure having the peripheral electrodeconnected with the four edges of the outer periphery of the secondelectrode, the peripheral electrode is preferably formed to be incontact substantially with the overall surfaces of the four edges of theouter periphery of the second electrode. According to this structure,current further readily flows from the second electrode toward theperipheral electrode along four directions, whereby the current can bemore uniformly dispersedly fed. Thus, the quantity of heat generated inthe second electrode can be further reduced as compared with a casewhere the current dispersedly flows along two directions of the secondelectrode.

In the aforementioned structure having the peripheral electrodeconnected with the four edges of the outer periphery of the secondelectrode, an edge of the second electrode corresponding to an edge ofthe peripheral electrode connected with the current source connectionterminal preferably includes a plurality of outlet terminals, theplurality of outlet terminals are preferably connected to the edge ofthe peripheral electrode connected with the current source connectionterminal, and the peripheral electrode is preferably formed to be incontact substantially with the overall surfaces of remaining three edgesof the second electrode. According to this structure, the secondelectrode and the peripheral electrode are connected with each other onfour edges, whereby current can be dispersedly fed from the secondelectrode to the peripheral electrode along four directions. Thus, heatgeneration of the second electrode can be further suppressed as comparedwith a case where the current is dispersed along two directions of thesecond electrode. Consequently, the emission layer can be effectivelyprevented from deterioration resulting from heat generation (temperaturerise) of the second electrode also when the display is increased insize. The plurality of outlet terminals provided on the edge of thesecond electrode are connected to the edge of the peripheral electrodeconnected with the current source connection terminal so that thecontact area between the plurality of outlet terminals and the edge ofthe peripheral electrode is reduced as compared with a case where oneedge of the second electrode and one edge of the peripheral electrodeare totally in contact with each other, whereby heat generated in thecurrent source connection terminal is further hardly transferred to thesecond electrode. Thus, the second electrode can be inhibited fromtemperature rise, whereby the emission layer can be prevented fromdeterioration resulting from temperature rise of the second electrode.In this case, the plurality of outlet terminals may be formed byprojecting portions of an irregular shape provided on the edge of thesecond electrode corresponding to the edge of the peripheral electrodeconnected with the current source connection terminal.

In the aforementioned structure having the peripheral electrodeconnected with the four edges of the outer periphery of the secondelectrode, the second electrode preferably includes a plurality ofoutlet terminals formed along four edges of the outer periphery of thesecond electrode, and the peripheral electrode is preferably connectedwith the four edges of the second electrode through the plurality ofoutlet terminals. According to this structure, the second electrode andthe peripheral electrode are connected with each other on four edges,whereby current can be uniformly dispersedly fed from the secondelectrode toward the peripheral electrode along four directions. Thus,heat generation of the second electrode can be further suppressed ascompared with a case where the current dispersedly flows along twodirections of the second electrode. Consequently, the emission layer canbe effectively prevented from deterioration resulting from heatgeneration (temperature rise) of the second electrode also when thedisplay is increased in size. The plurality of outlet terminals providedon the four edges of the second electrode are connected to four edges ofthe peripheral electrode so that the contact areas between the pluralityof outlet terminals and the four edges of the peripheral electrode arereduced as compared with a case of totally brining the four edges of thesecond electrode and the four edges of the peripheral electrode intocontact with each other, whereby heat generated in the current sourceconnection terminal is further hardly transferred to the secondelectrode. Thus, temperature rise of the second electrode can besuppressed, whereby the emission layer can be prevented fromdeterioration resulting from temperature rise of the second electrode.In this case, the plurality of outlet terminals may be formed byprojecting portions of irregular shapes provided on the four edges ofthe peripheral electrode.

The display according to the aforementioned aspect preferably furthercomprises cooling means provided in the vicinity of the current sourceconnection terminal. According to this structure, the cooling means caneffectively suppress heat generation of the current source connectionterminal readily subjected to concentration of current. Thus, thequantity of heat transferred from the current source connection terminalto the second electrode through the peripheral electrode can be reduced,whereby the emission layer can be further inhibited from deteriorationresulting from temperature rise of the second electrode. In this case,the cooling means preferably includes at least one of a fan, a coolingfin and a Peltier device. According to this structure, the currentsource connection terminal readily subjected to concentration of currentcan be easily inhibited from heat generation.

In the display according to the aforementioned aspect, the emissionlayer preferably includes an organic layer. According to this structure,the organic layer can be inhibited from deterioration resulting fromtemperature rise of the second electrode in an organic EL elementincluding the organic layer.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing the overall structure of an organic ELdisplay according to a first embodiment of the present invention;

FIG. 2 is a sectional view of the organic EL display according to thefirst embodiment taken along the line 100-100 in FIG. 1;

FIG. 3 is a plan view showing the overall structure of an organic ELdisplay according to a second embodiment of the present invention;

FIG. 4 is a sectional view of the organic EL display according to thesecond embodiment taken along the line 200-200 in FIG. 3;

FIG. 5 is a sectional view showing cooling means for a current supplyinput terminal of the organic EL display according to the secondembodiment shown in FIG. 3;

FIG. 6 is a plan view showing the overall structure of an organic ELdisplay according to a third embodiment of the present invention;

FIG. 7 is a sectional view of the organic EL display according to thethird embodiment taken along the line 300-300 in FIG. 6;

FIG. 8 is a plan view showing the overall structure of an organic ELdisplay according to a fourth embodiment of the present invention;

FIG. 9 is a plan view showing the overall structure of an organic ELdisplay according to a fifth embodiment of the present invention;

FIG. 10 is a sectional view showing a modification of the cooling meansfor the current supply input terminal of the organic EL displayaccording to the second embodiment shown in FIG. 5;

FIG. 11 is a sectional view showing another modification of the coolingmeans for the current supply input terminal of the organic EL displayaccording to the second embodiment shown in FIG. 5;

FIG. 12 is a perspective view showing the overall structure of aconventional organic EL display; and

FIG. 13 is a plan view showing the overall structure of the conventionalorganic EL display shown in FIG. 12.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are now described with reference tothe drawings.

First Embodiment

Referring to FIGS. 1 and 2, anodes 2 consisting of transparent metaloxide films of ITO (indium-tin oxide) or the like having a thickness ofabout 100 nm are formed on a glass substrate 1 in an organic EL displayaccording to a first embodiment of the present invention. Organic layers5 are formed on the anodes 2. The organic layers 5 consist of holeinjection layers formed on the anodes 2, hole transport layers formed onthe hole injection layers and emission layers formed on the holetransport layers. A cathode 3 consisting of a low work function materialsuch as MgIn having a thickness of about 300 nm is formed on the organiclayers 5 to cover the overall structure.

The glass substrate 1 is an example of the “substrate” according to thepresent invention. The anodes 2 are examples of the “first electrode”according to the present invention, and the cathode 3 is an example ofthe “second electrode” according to the present invention. The organiclayers 5 are examples of the “emission layer” according to the presentinvention.

According to the first embodiment, an annular peripheral electrode 7 ofMg having a smaller sheet resistance value than the cathode 3 is formedto enclose the outer periphery 3 a of the cathode 3. This annularperipheral electrode 7 is formed to be in contact with the side surfacesof all four edges of the outer periphery 3 a of the cathode 3. Theannular peripheral electrode 7 is formed to be in contact with the uppersurface of the glass substrate 1. A current supply input terminal 8connected with an external current source is connected to the outerperiphery of the peripheral electrode 7. The current supply inputterminal 8 is an example of the “current source connection terminal”according to the present invention.

Drive circuits 6 a and 6 b are arranged on the glass substrate 1. Videosignal lines 51 are connected to the drive circuit 6 a. Scanning lines52 and power supply lines 53 are connected to the drive circuit 6 b. Aninsulator 9 is embedded between each adjacent pair of pixels, as shownin FIG. 2.

According to the first embodiment, as hereinabove described, the annularperipheral electrode 7 consisting of the material having a smaller sheetresistance value than the cathode 3 is provided to be connected with allfour edges of the outer periphery 3 a of the cathode 3, whereby currentreadily flows from the cathode 3 toward the peripheral electrode 7 andthis current can be uniformly dispersedly fed along four directions.Thus, heat generation of the cathode 3 can be further suppressed ascompared with a case where the current dispersedly flows along twodirections of the cathode 3. Consequently, the emission layers can beeffectively prevented from deterioration resulting from heat generation(temperature rise) of the cathode 3 also when the organic EL display isincreased in size.

According to the first embodiment, the current supply input terminal 8connected with the external current source is provided on the outerperiphery of the annular peripheral electrode 7 arranged to enclose theouter periphery 3 a of the cathode 3, whereby the cathode 3 can beeasily electrically connected with the single current supply inputterminal 8 through the annular peripheral electrode 7. Consequently, theorganic EL display can be easily connected with the external currentsource through the single current supply input terminal 8 also whenconnected with the external current source on a single portion.

According to the first embodiment, the current supply input terminal 8is provided on the outer periphery of the peripheral electrode 7 forincreasing the distance between the current supply input terminal 8 andthe cathode 3 by the width of the peripheral electrode 7, whereby heatgenerated in the current supply input terminal 8 readily subjected toconcentration of current is hardly transferred to the cathode 3. Thus,the organic layers 5 can be inhibited from deterioration resulting fromtemperature rise of the cathode 3.

Second Embodiment

Referring to FIGS. 3 to 5, an opening 20 is provided between an edge ofa peripheral electrode 7 connected with a current supply terminal 8 anda corresponding edge of a cathode 13 in an organic EL display accordingto a second embodiment of the present invention while mounting a coolingfin 14 on the current supply terminal 8 in a structure similar to thatof the first embodiment shown in FIG. 1. The remaining structure of theorganic EL display according to the second embodiment is similar to thatof the aforementioned organic EL display according to the firstembodiment. The organic EL display according to the second embodiment isnow described in detail.

In the organic EL display according to the second embodiment, anodes 2of ITO or the like are formed on a glass substrate 1, similarly to theaforementioned first embodiment. Organic layers 5 consisting of holeinjection layers, hole transport layers and emission layers in ascendingorder are formed on the anodes 2. An insulator 9 is embedded betweeneach adjacent pair of pixel parts.

The cathode 13 is formed to cover a plurality of pixel parts. Thecathode 13 is an example of the “second electrode” according to thepresent invention. The annular peripheral electrode 7 of a material (Mg)having a lower sheet resistance value than the cathode 13 is formed toenclose the cathode 13. The current supply input terminal 8 is connectedto one edge of the outer periphery of the peripheral electrode 7.

According to the second embodiment, the opening 20 is formed between theedge of the peripheral electrode 7 connected with the current supplyinput terminal 8 and the corresponding edge of the cathode 13. Sidesurfaces of three edges of the outer periphery 13 a of the cathode 13and corresponding three edges of the peripheral electrode 7 are totallyin contact with each other. The peripheral electrode 7 is formed to bein contact with the upper surface of the glass substrate 1. According tothe second embodiment, the cooling fin 14 is provided under the currentsupply input terminal 8, as shown in FIG. 5. The cooling fin 14 is anexample of the “cooling means” according to the present invention.

According to the second embodiment, as hereinabove described, theopening 20 is so provided that the cathode 13 can be effectivelyprevented from transfer of heat generated in the current supply inputterminal 8 readily subjected to concentration of current. Thus, thecathode 13 can be prevented from temperature rise, whereby the organiclayers 5 can be inhibited from deterioration resulting from temperaturerise of the cathode 13.

According to the second embodiment, three edges of the outer periphery13 a of the cathode 13 are totally in contact with three edges of theperipheral electrode 7, whereby current can be dispersedly fed from thecathode 13 to the peripheral electrode 7 along three directions. Thus,heat generation of the cathode 13 can be further suppressed as comparedwith a case where the current dispersedly flows along two directions ofthe cathode 13. Consequently, the organic layers 5 can be effectivelyprevented from deterioration resulting from heat generation (temperaturerise) of the cathode 13 also when the organic EL display is increased insize.

According to the second embodiment, further, the cooling fin 14 isprovided under the current supply input terminal 8, whereby heatgeneration of the current supply input terminal 8 readily subjected toconcentration of current can be effectively suppressed. Consequently,the quantity of heat transferred from the current supply input terminal8 to the cathode 13 through the peripheral electrode 7 can be reduced.Thus, the organic layers 5 can be further inhibited from deteriorationresulting from temperature rise of the cathode 13.

According to the second embodiment, in addition, the current supplyinput terminal 8 connected with the external current source is providedon the outer periphery of the annular peripheral electrode 7 arranged toenclose the outer periphery 13 a of the cathode 13, whereby the cathode13 can be easily electrically connected with the single current supplyinput terminal 8 through the annular peripheral electrode 7.Consequently, the organic EL display can be easily connected with theexternal current source through the single current supply input terminal8 also when connected with the external current source on a singleportion.

Third Embodiment

Referring to FIGS. 6 and 7, a cathode 23 and a peripheral electrode 7are totally in contact with each other on three edges of the cathode 23while one edge of the cathode 23 is connected to the peripheralelectrode 7 through a plurality of outlet terminals 23 b in an organicEL display according to a third embodiment of the present invention. Theremaining structure of the organic EL display according to the thirdembodiment is similar to that of the aforementioned organic EL displayaccording to the first embodiment.

According to the third embodiment, an edge of the cathode 23corresponding to an edge of the peripheral electrode 7 connected with acurrent supply input terminal 8 is irregularly formed for forming theplurality of outlet terminals 23 b by projecting portions of theirregular shape. The edge of the peripheral electrode 7 connected withthe current supply input terminal 8 is connected with one edge of thecathode 23 through the plurality of outlet terminals 23 b. The remainingthree edges of the outer periphery 23 a of the cathode 23 are formed tobe totally in contact with the peripheral electrode 7. The cathode 23 isan example of the “second electrode” according to the present invention.

According to the third embodiment, as hereinabove described, theperipheral electrode 7 and the cathode 23 are connected with each otherthrough the overall surfaces of the three edges of the cathode 23 andthe plurality of outlet terminals 23 b provided on the remaining edge,whereby current flowing to the cathode 23 can be substantially uniformlyfed along four directions. Thus, heat generation of the cathode 23 canbe further suppressed as compared with a case where the currentdispersedly flows along two directions of the cathode 23. Consequently,emission layers can be effectively prevented from deteriorationresulting from heat generation (temperature rise) of the cathode 23 alsowhen the organic EL display is increased in size.

According to the third embodiment, the edge of the peripheral electrode7 connected with the current supply input terminal 8 and thecorresponding edge of the cathode 23 are connected with each otherthrough the plurality of outlet terminals 23 b, whereby the contact areacan be reduced as compared with a case of totally bringing the cathode23 and the peripheral electrode 7 into contact with each other. Thus,the quantity of heat generated in the current supply input terminal 8readily subjected to concentration of current and transferred to thecathode 23 can be reduced. Thus, organic layers 5 can be effectivelyprevented from deterioration resulting from temperature rise of thecathode 23.

According to the third embodiment, further, the current supply inputterminal 8 connected with the external current source is provided on theouter periphery of the annular peripheral electrode 7 arranged toenclose the outer periphery of the cathode 23, whereby the cathode 23can be easily electrically connected with the single current supplyinput terminal 8 through the annular peripheral electrode 7.Consequently, the organic EL display can be easily connected with theexternal current source through the single current supply input terminal8 also when connected with the external current source on a singleportion.

Fourth Embodiment

Referring to FIG. 8, an opening 40 is provided between an edge of aperipheral electrode 7 connected with a current supply input terminal 8and a corresponding edge 33 c of a cathode 33 while other two edges ofthe cathode 33 are connected to the peripheral electrode 7 through aplurality of outlet terminals 33 b and the remaining edge 33 a of thecathode 33 is totally brought into contact with the peripheral electrode7 in an organic EL display according to a fourth embodiment of thepresent invention. The remaining structure of the organic EL displayaccording to the fourth embodiment is similar to that of the organic ELdisplay according to the first embodiment. The organic EL displayaccording to the fourth embodiment is now described in detail.

In the organic EL display according to the fourth embodiment, theopening 40 is provided between the edge of the peripheral electrode 7connected with the current supply input terminal 8 and the correspondingedge 33 c of the cathode 33. The plurality of outlet terminals 33 bconsisting of projecting portions of irregular shapes are formed onother two edges of the cathode 33 at prescribed intervals. These twoedges of the cathode 33 and two edges of the peripheral electrode 7 areconnected with each other through the plurality of outlet terminals 33b. The remaining edge 33 a of the cathode 33 is totally brought intocontact with the remaining edge of the peripheral electrode 7. Thecathode 33 is an example of the “second electrode” according to thepresent invention.

According to the fourth embodiment, as hereinabove described, thecontact area between the cathode 33 and the peripheral electrode 7 isincreased as receding from the current supply input terminal 8. In otherwords, the opening 40 is formed on the edge 33 c of the cathode 33closest the current supply input terminal 8 while the two edges of thecathode 33 secondly closest thereto are connected with the peripheralelectrode 7 through the plurality of outlet terminals 33 b, and the edge33 a of the cathode 33 farthest from the current supply input terminal 8is totally brought into contact with the corresponding edge of theperipheral electrode 7.

According to the fourth embodiment, as hereinabove described, thecontact area between the cathode 33 and the peripheral electrode 7 isincreased as receding from the current supply input terminal 8, wherebythe cathode 33 can be further effectively prevented from transfer ofheat readily generated in the current supply input terminal 8. Thus, thecathode 33 can be prevented from temperature rise, whereby organiclayers 5 can be prevented from deterioration resulting from temperaturerise of the cathode 33.

According to the fourth embodiment, further, the cathode 33 and theperipheral electrode 7 are in contact with each other on three edges ofthe cathode 33 and the corresponding three edges of the peripheralelectrode 7, whereby current dispersedly flows from the cathode 33toward the peripheral electrode 7 along three directions. Therefore,heat generation of the cathode 33 can be further suppressed as comparedwith a case where the current dispersedly flows along two directions ofthe cathode 33. Thus, emission layers can be prevented fromdeterioration resulting from temperature rise of the cathode 33.

According to the fourth embodiment, in addition, the current supplyinput terminal 8 connected with the external current source is providedon the outer periphery of the annular peripheral electrode 7 arranged toenclose the outer periphery of the cathode 33, whereby the cathode 33can be easily electrically connected with the single current supplyinput terminal 8 through the annular peripheral electrode 7.Consequently, the organic EL display can be easily connected with theexternal current source through the single current supply input terminal8 also when connected with the external current source on a singleportion.

Fifth Embodiment

Referring to FIG. 9, a plurality of outlet terminals 43 a are formed onall of four edges of a cathode 43 at prescribed intervals for connectingfour edges of the cathode 43 with corresponding four edges of aperipheral electrode 7 through the outlet terminals 43 a in an organicEL display according to a fifth embodiment of the present invention. Theremaining structure of the organic EL display according to the fifthembodiment is similar to that of the organic EL display according to thefirst embodiment.

According to the fifth embodiment, the plurality of outlet terminals 43a consisting of projecting portions of irregular shapes are provided atprescribed intervals along four edges of the cathode 43. Four edges ofthe cathode 43 are connected with the corresponding four edges of theperipheral electrode 7 through the plurality of outlet terminals 43 a.The cathode 43 is an example of the “second electrode” according to thepresent invention.

According to the fifth embodiment, as hereinabove described, four edgesof the cathode 43 are connected with the corresponding four edges of theperipheral electrode 7 through the plurality of outlet terminals 43 a,whereby current flowing from the cathode 43 toward the peripheralelectrode 7 can be uniformly dispersed along four directions. Thus, heatgeneration of the cathode 43 can be further suppressed as compared witha case where the current dispersedly flows along two directions of thecathode 43. Consequently, emission layers can be effectively preventedfrom deterioration resulting from heat generation (temperature rise) ofthe cathode 43 also when the organic EL display is increased in size.

According to the fifth embodiment, the cathode 43 and the peripheralelectrode 7 are connected with each other through the plurality ofoutlet terminals 43 a so that the contact area between the cathode 43and the peripheral electrode 7 can be reduced as compared with a case oftotally bringing the cathode 43 and the peripheral electrode 7 intocontact with each other. When a current supply input terminal 8generates heat, therefore, the heat can be rendered hardly transferableto the cathode 43. Thus, the cathode 43 can be prevented fromtemperature rise. Therefore, organic layers 5 can be effectivelyprevented from deterioration resulting from temperature rise of thecathode 43.

According to the fifth embodiment, the current supply input terminal 8connected with an external current source is provided on the outerperiphery of the annular peripheral electrode 7 arranged to enclose theouter periphery of the cathode 43 so that the cathode 43 can be easilyelectrically connected with the single current supply input terminal 8through the annular peripheral electrode 7. Consequently, the organic ELdisplay can be easily connected with the external current source throughthe single current supply input terminal 8 also when connected with theexternal current source on a single portion.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

While the display according to the present invention is applied to anorganic EL display in each of the aforementioned embodiments, forexample, the present invention is not restricted to this but is alsoapplicable to a display, other than the organic EL display, includingemission layers.

While the peripheral electrode 7 is made of Mg in each of theaforementioned embodiments, the present invention is not restricted tothis but another material may alternatively be employed so far as thesheet resistance value thereof is smaller than that of the cathode. Forexample, Ti or Al is conceivably employable as the material for theperipheral electrode 7. Alternatively, a binary alloy or a ternary alloyof Al—Ti, Al—Cr, Al—Mo, Al—W, Al—Ta, Al—Cu or Al—Nd may be employed.

While the anodes are arranged under the organic layers and the cathodeis arranged on the organic layers in each of the aforementionedembodiments, the present invention is not restricted to this but theanodes may alternatively be arranged on the organic layers and thecathode may alternatively be arranged under the organic layers.

While the cooling fin 14 is employed in the aforementioned secondembodiment as the cooling means for the current supply input terminal 8,the present invention is not restricted to this but another coolingmeans may alternatively be employed. For example, a fan 15 may beprovided under a current supply input terminal 8 as shown in FIG. 10, ora Peltier device 16 may be provided as a cooling element under a currentsupply input terminal 8 as shown in FIG. 11. According to thisstructure, the current supply input terminal 8 readily generating heatdue to concentration of current can be easily cooled, whereby thequantity of heat transferred from the power supply input terminal 8 tothe cathode 13 through the peripheral electrode 7 can be reduced.Consequently, the organic layers 5 can be further inhibited fromdeterioration resulting from temperature rise of the cathode 13.

1. A display comprising: a first electrode formed on a substrate; anemission layer formed on said first electrode; a second electrode havingan outer periphery defined by side surfaces formed on said emissionlayer; a peripheral electrode, arranged to enclose the outer peripheryof said second electrode and connected with four side surfaces of theouter periphery of said second electrode, having a smaller sheetresistance value than said second electrode; and a current sourceconnection terminal connected to the outer periphery of said peripheralelectrode, wherein said second electrode is formed to cover not only anupper surface, but also a side surface of said emission layer.
 2. Thedisplay according to claim 1 wherein said peripheral electrode is formedto be in contact substantially with the overall surfaces of said fourside surfaces of the outer periphery of said second electrode.
 3. Adisplay comprising: a first electrode formed on a substrate; an emissionlayer formed on said first electrode; a second electrode formed on saidemission layer, the second electrode is formed to cover not only anupper surface, but also a side surface of said emission layer; aperipheral electrode, arranged to enclose the outer periphery of saidsecond electrode and connected with at least three edges of the outerperiphery of said second electrode, having a smaller sheet resistancevalue than said second electrode; and a current source connectionterminal connected to the outer periphery of said peripheral electrode,wherein said emission layer includes an organic layer.
 4. A displaycomprising: a first electrode formed on a substrate; an emission layerformed on said first electrode; a second electrode formed on saidemission layer, the second electrode is formed to cover not only anupper surface, but also a side surface of said emission layer; aperipheral electrode, arranged to enclose the outer periphery of saidsecond electrode and connected with at least three edges of the outerperiphery of said second electrode, having a smaller sheet resistancevalue than said second electrode; and a current source connectionterminal connected to the outer periphery of said peripheral electrode,wherein the display includes a plurality of pixels.